1. Field of the Invention
The present invention relates to a valve operating control system for an engine, including a first valve-operating characteristic changing mechanism adapted to change the valve lift, and a second valve-operating characteristic changing mechanism adapted to change the valve timing.
2. Description of the Related Art
There is a conventionally known valve operating control system for an engine, which includes a valve-operating characteristic changing mechanism provided between a camshaft and a sprocket for driving the camshaft, so that the phase of the sprocket relative to the camshaft is changed in accordance with the operational state of the engine to change the valve timing. There is also such a valve operating control system known from Japanese Patent Application Laid-open No. 9-209722, in which an advance oil chamber and a delay oil chamber are formed in a camshaft supporting portion.
In an engine including a first valve-operating characteristic changing mechanism adapted to change the valve lift in accordance with the operational state of the engine, and a second valve-operating characteristic changing mechanism adapted to change the valve timing in accordance with the operational state of the engine, the first valve-operating characteristic changing mechanism is mounted on a rocker arm supported on a rocker arm shaft, and the second valve-operating characteristic changing mechanism is mounted at an end of a camshaft. For this reason, it is required that a control oil passage leading to the first valve-operating characteristic changing mechanism and an advance oil passage and a delay oil passage leading to the second valve-operating characteristic changing mechanism are defined in a camshaft support member for supporting the camshaft and the rocker arm shaft. However, the camshaft support member is provided with bolts bores for fastening the camshaft support member and for this reason, it is difficult to secure a sufficient sectional area of a flow path in each of the control oil passage, the advance oil passage and the delay oil passage without an increase in size of the camshaft support member and while avoiding the interference with the bolts bores, and there is a possibility that the sectional area of each of the oil passages is insufficient, resulting in a degraded responsiveness of each of the first and second valve-operating characteristic changing mechanism.
Accordingly, it is an object of the present invention to ensure that the oil passages leading to the first valve-operating characteristic changing mechanism adapted to change the valve lift and the second valve-operating characteristic changing mechanism adapted to change the valve timing are defined compactly in the camshaft support member.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a valve operating control system for an engine, including a first valve-operating characteristic changing mechanism adapted to change the valve lift, and a second valve-operating characteristic changing mechanism adapted to change the valve timing, wherein a pair of valve-timing controlling oil passages leading to the second valve-operating characteristic changing mechanism are defined in a camshaft support member, and a valve lift controlling oil passage leading to the first valve-operating characteristic changing mechanism is defined between the pair of valve-timing controlling oil passages in a mating surface of the camshaft support member with another member.
With the above arrangement, the pair of valve-timing controlling oil passages leading to the second valve-operating characteristic changing mechanism and the valve lift controlling oil passage leading to the first valve-operating characteristic changing mechanism are defined in the camshaft support member, and the valve lift controlling oil passage is defined between the pair of valve-timing controlling oil passages in the mating surface of the camshaft support member with another member. Therefore, the pair of valve-timing controlling oil passages and the valve lift controlling oil passage can be formed compactly in the camshaft support member, so that they do not interfere with each other.
According to a second aspect and feature of the present invention, in addition to the first feature, the depth of the valve lift controlling oil passage in a position where the valve lift controlling oil passage and the pair of valve-timing controlling oil passages are overlapped on each other as viewed in an axial direction of a camshaft is larger than that in the other positions.
With the above arrangement, even if the width of the valve lift controlling oil passage is reduced in the position where the valve lift controlling oil passage and the pair of valve-timing controlling oil passages are overlapped on each other as viewed in the axial direction of the camshaft in order to avoid the interference with the valve-timing controlling oil passages, it is possible to secure a sectional area of a flow path in the valve lift controlling oil passage without an increase in size of the camshaft support member, because the depth of the valve lift controlling oil passage is larger than that in the other positions.
According to a third aspect and feature of the present invention, in addition to the first or second feature, the camshaft support member is fastened to another member by bolts; the pair of valve-timing controlling oil passages are defined in the mating surface of the camshaft support member with another member, and the depths of the pair of valve-timing controlling oil passages in a position where the pair of valve-timing controlling oil passages and the bolts are overlapped on each other as viewed in the axial direction of the camshaft are larger than those in the other positions.
With the above arrangement, even if the pair of valve-timing controlling oil passages are defined in the mating surface of the camshaft support member fastened to another member by the bolts, and the widths of the valve-timing controlling oil passages in the position where the pair of valve-timing controlling oil passages and the bolts are overlapped on each other as viewed in the axial direction of the camshaft are larger than those in other positions, it is possible to secure a sectional area of a flow path in each of the valve-timing controlling oil passages without an increase in size of the camshaft support member, because the depths of the valve-timing controlling oil passages are larger than those in the other positions.
According to a fourth aspect and feature of the present invention, in addition to any of the first to third features, the camshaft support member includes a support portion for a rocker arm shaft, and the pair of valve-timing controlling oil passages are defined in the vicinity of the support portion.
With the above arrangement, the pair of valve-timing controlling oil passages are defined in the vicinity of the support portion for the rocker arm shaft and hence, the support portion is reinforced by a cylindrical portion defining the valve-timing controlling oil passages, leading to an enhanced supported rigidity of the rocker arm shaft.
According to a fifth aspect and feature of the present invention, in addition to the first feature, the width of the valve lift controlling oil passage in a longitudinal direction of the camshaft in a position where the valve lift controlling oil passage and the pair of valve-timing controlling oil passages are overlapped on each other as viewed in the axial direction of the camshaft is smaller than that in the other positions.
With the above arrangement, the width of the valve lift controlling oil passage in the longitudinal direction of the camshaft in the position where the valve lift controlling oil passages and the pair of valve-timing controlling oil passages are overlapped on each other as viewed in the axial direction of the camshaft is smaller than that in other positions. Therefore, the pair of valve-timing controlling oil passages can be disposed in proximity to each other to contribute to the compactness of the camshaft support member.
According to a sixth aspect and feature of the present invention, in addition to the first feature, the camshaft support member is fastened to another member by bolts; the pair of valve-timing controlling oil passages are defined in the mating surface of the camshaft support member with another member, and the widths of the pair of valve-timing controlling oil passages in a longitudinal direction of the camshaft in a position where the pair of valve-timing controlling oil passages and the bolts are overlapped on each other as viewed in the axial direction of the camshaft are smaller than those in the other positions.
With the above arrangement, in the position where the pair of the valve-timing controlling oil passages defined in the mating surface of the camshaft support member with another member is overlapped on the bolts for fastening the camshaft support member to another member as viewed in the axial direction of the camshaft, the widths of the pair of valve-timing controlling oil passages are smaller than those in the other positions. Therefore, the pair of valve-timing controlling oil passages can be disposed in proximity to each other to contribute to the compactness of the camshaft support member.
According to a seventh aspect and feature of the present invention, in addition to the first, second or fifth feature, the position where the valve lift controlling oil passage and the pair of valve-timing controlling oil passages are overlapped on each other as viewed in the axial direction of the camshaft is between the bolts for fastening the camshaft support member mounted between a plurality of the camshafts to the cylinder head.
With the above arrangement, the position where the valve lift controlling oil passage and the pair of valve-timing controlling oil passages are overlapped on each other as viewed in the axial direction of the camshaft is between the bolts for fastening the camshaft support member mounted between the plurality of camshafts to the cylinder head. Therefore, it is possible to effectively inhibit the leakage of oil between the valve lift controlling oil passage and the pair of valve-timing controlling oil passages by fastening forces of the bolts.
An intake camshaft 12 in an embodiment corresponds to the camshaft of the present invention; a lower camshaft holder 25 in the embodiment corresponds to the camshaft support member of the present invention; an intake rocker arm shaft 32 in the embodiment corresponds to the rocker arm shaft of the present invention; an oil passage P11 in the embodiment corresponds to the valve lift controlling oil passage of the present invention; and oil passages P18a, P18b, P19a and P19b in the embodiment correspond to the valve-timing controlling oil passages of the present invention. In addition, a cylinder head 23 in the embodiment corresponds to another member in claims of the present invention, and an upper camshaft holder 26 in the embodiment corresponds to another member in claim 3 of the present invention.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.